article: Tomorrow is August fourth. It is Peter's grandfather's birthday. It is his 73rd  birthday. Peter and his two sisters, Sally and Tina buy some things for their grandfather this afternoon. Sally buys a nice birthday card. And she writes "Happy birthday" on it. Tina buys a blue shirt from a clothes store. It is $29. Peter buys some fruit and a set of books. They are $39 .The name of the books is Harry Potter. His grandfather likes reading a lot. Peter hopes he will like the books.
question: What does Sally buy for her grandfather?
options: some fruit A blue shirt A birthday card A set of books